909 resultados para migration of rhizobia


Relevância:

80.00% 80.00%

Publicador:

Resumo:

我国曾经记录有(鱼芒)科鱼类4种.国际上近年来对(鱼芒)科鱼类的分类进行了许多重要的修订,物种数量已达3属22种.我国的(鱼芒)科鱼类也因长时间没有进行及时的分类修订而存在许多疑问.基于国内自1960年以来所收集的珍贵标本和记录,确认我国记录有(鱼芒)科鱼类1属3种.它们是:长丝(鱼芒)(Pangasius sanitwongsei Smith)、贾巴(鱼芒)(Pangasius djambal Bleeker)、短须(鱼芒)(Pangasius micronemus Bleeker).在此基础上,根据掌握的资料对我国(鱼芒)科鱼类的种群现状和濒危原因、洄游的性质及洄游群体数量下降原因以及水电站建设对大型洄游鱼类的影响进行了分析.以往记录显示,捕获时间都集中于4-5月份,无冬季捕获记录.捕获季节与(鱼芒)科鱼类产卵繁殖季节高度吻合,提示其上溯到我国澜沧江下游应属生殖洄游,而不是索饵洄游.被捕获记录主要出现于20世纪60-70年代,之后则数量锐减.导致这种情况发生的主要原因可能有三方面:1)下游湄公河对(鱼芒)科鱼类的捕捞压力过大;2)湄公河-澜沧江航运船只对(鱼芒)科鱼类有损害作用;3)由于西南季风变化的影响,澜沧江径流量发生变化,可能间接导致(鱼芒)科鱼类洄游行为发生改变.分析显示,(鱼芒)科鱼类的洄游与3-4月份澜沧江流量呈密切相关规律,提示适合鱼类产卵的雨季及西南夏季风比往年较早到达该地区,从而激发它们较往年提前启动生殖洄游,并且溯河的高度较高.以往的捕获记录还表明,(鱼芒)科鱼类主要洄游至景洪下方的澜沧江河段及支流补远江,上述水域是其喜好的产卵场之一.景洪大桥以下的干支流不适合建设水电站,因为电站大坝必然会阻断(鱼芒)科鱼类的繁殖洄游,影响其繁殖活动.而景洪大桥上方的干流电站不在(鱼芒)科鱼类正常繁殖洄游通道中,大坝阻隔作用对(鱼芒)科鱼类的影响相对较小.建议把补远江建设成为鱼类和水生生物保护区.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Ferroic-order parameters are useful as state variables in non-volatile information storage media because they show a hysteretic dependence on their electric or magnetic field. Coupling ferroics with quantum-mechanical tunnelling allows a simple and fast readout of the stored information through the influence of ferroic orders on the tunnel current. For example, data in magnetic random-access memories are stored in the relative alignment of two ferromagnetic electrodes separated by a non-magnetic tunnel barrier, and data readout is accomplished by a tunnel current measurement. However, such devices based on tunnel magnetoresistance typically exhibit OFF/ON ratios of less than 4, and require high powers for write operations (>1 × 10(6) A cm(-2)). Here, we report non-volatile memories with OFF/ON ratios as high as 100 and write powers as low as ∼1 × 10(4) A cm(-2) at room temperature by storing data in the electric polarization direction of a ferroelectric tunnel barrier. The junctions show large, stable, reproducible and reliable tunnel electroresistance, with resistance switching occurring at the coercive voltage of ferroelectric switching. These ferroelectric devices emerge as an alternative to other resistive memories, and have the advantage of not being based on voltage-induced migration of matter at the nanoscale, but on a purely electronic mechanism.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Ferroic-order parameters are useful as state variables in non-volatile information storage media because they show a hysteretic dependence on their electric or magnetic field. Coupling ferroics with quantum-mechanical tunnelling allows a simple and fast readout of the stored information through the influence of ferroic orders on the tunnel current. For example, data in magnetic random-access memories are stored in the relative alignment of two ferromagnetic electrodes separated by a non-magnetic tunnel barrier, and data readout is accomplished by a tunnel current measurement. However, such devices based on tunnel magnetoresistance typically exhibit OFF/ON ratios of less than 4, and require high powers for write operations (>1 × 10 6 A cm -2). Here, we report non-volatile memories with OFF/ON ratios as high as 100 and write powers as low as ∼1 × 10 4A cm -2 at room temperature by storing data in the electric polarization direction of a ferroelectric tunnel barrier. The junctions show large, stable, reproducible and reliable tunnel electroresistance, with resistance switching occurring at the coercive voltage of ferroelectric switching. These ferroelectric devices emerge as an alternative to other resistive memories, and have the advantage of not being based on voltage-induced migration of matter at the nanoscale, but on a purely electronic mechanism. © 2012 Macmillan Publishers Limited. All rights reserved.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Board-level optical links are an attractive alternative to their electrical counterparts as they provide higher bandwidth and lower power consumption at high data rates. However, on-board optical technology has to be cost-effective to be commercially deployed. This study presents a chip-to-chip optical interconnect formed on an optoelectronic printed circuit board that uses a simple optical coupling scheme, cost-effective materials and is compatible with well-established manufacturing processes common to the electronics industry. Details of the link architecture, modelling studies of the link's frequency response, characterisation of optical coupling efficiencies and dynamic performance studies of this proof-of-concept chip-to-chip optical interconnect are reported. The fully assembled link exhibits a -3 dBe bandwidth of 9 GHz and -3 dBo tolerances to transverse component misalignments of ±25 and ±37 μm at the input and output waveguide interfaces, respectively. The link has a total insertion loss of 6 dBo and achieves error-free transmission at a 10 Gb/s data rate with a power margin of 11.6 dBo for a bit-error-rate of 10 -12. The proposed architecture demonstrates an integration approach for high-speed board-level chip-to-chip optical links that emphasises component simplicity and manufacturability crucial to the migration of such technology into real-world commercial systems. © 2012 The Institution of Engineering and Technology.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Ground improvement techniques can be adopted to prevent existing buildings built on liquefiable soils sustaining damage in future earthquakes. Impermeable geomembrane containment walls may be an economic and successful technique but their design and performance are currently not well defined or well understood for this application. This paper describes centrifuge testing carried out to investigate the performance of such containment walls as a liquefaction remediation method for a single degree of freedom frame structure. The results were compared with those from similar centrifuge testing carried out with the same structure founded on unimproved sand, to assess the effectiveness of the remediation method. It was found that the geomembrane containment walls tested were effective at reducing structural settlement and did not significantly increase the accelerations transmitted to the structure. Structural settlements were reduced primarily by mobilising hoop stress and preventing lateral soil movement. By preventing surface drainage, a decrease in the volume change of the foundation sand was also observed. In addition, the impermeability of the walls may be important as this prevented rapid migration of pore water fromthe free field to the foundation region.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Diagonal self-assembled InAs quantum wire (QWR) arrays with the stacked InAs/In0.52Al0.48As structure are grown on InP substrates, which are (001)-oriented and misoriented by 6degrees towards the [100] direction. Both the molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE) techniques are employed. Transmission electron microscopy reveals that whether a diagonal InAs QWR array of the stacked InAs/InAlAs is symmetrical about the growth direction or not depends on the growth method as well as substrate orientation. Asymmetry in the diagonal MEE-grown InAs QWR array can be ascribed to the influence of surface reconstruction on upward migration of adatoms during the self-assembly of the InAs quantum wires.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Fabrication of semiconductor nanostructures such as quantum dots (QDs), quantum rings (QRs) has been considered as the important step for realization of solid state quantum information devices, including QDs single photon emission source, QRs single electron memory unit, etc. To fabricate GaAs quantum rings, we use Molecular Beam Epitaxy (MBE) droplet technique in this report. In this droplet technique, Gallium (Ga) molecular beams are supplied initially without Arsenic (As) ambience, forming droplet-like nano-clusters of Ga atoms on the substrate, then the Arsenic beams are supplied to crystallize the Ga droplets into GaAs crystals. Because the morphologies and dimensions of the GaAs crystal are governed by the interplay between the surface migration of Ga and As adatoms and their crystallization, the shape of the GaAs crystals can be modified into rings, and the size and density can be controlled by varying the growth temperatures and As/Ga flux beam equivalent pressures(BEPs). It has been shown by Atomic force microscope (AFM) measurements that GaAs single rings, concentric double rings and coupled double rings are grown successfully at typical growth temperatures of 200 C to 300 C under As flux (BEP) of about 1.0 x 10(-6) Torr. The diameter of GaAs rings is about 30-50 nm and thickness several nm.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

现代人起源和史前迁移问题的遗传学研究是一个受到广泛关注的研究领 域。首先,它可以解答人类所关心的关于自身的起源以及我们祖先的史前活动问 题;其次,现代人祖先分开并扩散到世界各地,由于受到不同的外界环境和不同 的历史事件的影响,遗传上发生相应的变化,形成现有人群之间不仅在外表上存 在差异,同时在对疾病的易感性方面也存在差异。近年来的研究还发现,不同人 群之间在对药物的反应上也存在差异。 因此,人群起源与史前迁移研究对生物 医学研究也至关重要。目前,世界各地人群的起源和史前迁移问题的研究已经取 得很多进展,东亚之外的其它各个地区现有人群的起源和迁移已经相当清楚,东 亚现代人的起源对完整回答现代人的起源问题至关重要。 东亚现代人史前早期迁移的问题还存在很大争议,对现有研究结果的解释 甚至存在冲突。通过对东亚地区现有人群展开系统采样,并对东亚特有的Y 单 倍型遗传标记进行扫描,以东亚现代人特有的单倍型组O3-M122 下的各个特征 位点为遗传标记,我们对来自东亚地区的2332 份男性样本进行了研究。结果发 现,O3-M122 单倍型组为东亚现代人群的主导单倍型,其平均频率是44.3%。 以SNPs 突变特征为背景,展开SNPs-STRs 相结合的研究,通过大量的分析和统 计检验,从STRs 数据上可以看出东亚现代人南部人群的O3-M122 单倍型组的 多样性比北方人群高。这一证据揭示出东亚现代人特有单倍型O3-M122 突变为 东亚南部起源,然后随着东亚现代人早期的由南向北迁移活动而扩散到北方。利 用SNPs-STRs 相结合的遗传学分析手段,推导出东亚特有单倍型组O3-M122 伴 随人群由南向北的早期迁移事件发生于距今约25000~30000 年以前,这一结论 与东亚现代人的化石证据推断的结论相一致。O3-M122 单倍型组的史前早期迁 移事件有助于从遗传学角度透视东亚现代人早期迁移的路线和起源问题。 东亚地区现代人史前迁移活动遗留下神秘的悬棺文化一直令人费解,考古学的推论存在很大争议。我们利用遗传学手段对现存悬棺文化的保留人群展开研 究,采用父系和母系遗传标记相结合的方法探讨悬棺文化的传播人群的族源。从 遗传上看,悬棺葬俗的拥有人群不论从母系还是父系遗传学证据都为典型的东亚 南方人群。 为最终解决东亚现代人起源和史前迁移问题,我们对考古发掘出来的东亚 地区现代人化石展开古DNA(ancient DNA, aDNA)研究。目前,aDNA 分析的 技术和手段已经建立并逐步成熟,并且积累了一定量的东亚现代人的aDNA 数 据,这一研究还在继续。aDNA 最终会为解答东亚现代人起源和史前迁移问题提 供强有力的遗传学证据。

Relevância:

80.00% 80.00%

Publicador:

Resumo:

由于伦理和材料来源的限制,目前对灵长类早期神经发育缺乏深入地了解。与啮齿类动物相比,猕猴在遗传和生理上与人类更接近,因此猕猴胚胎干细胞(rESCs)研究具有重要的研究价值,不仅能为研究发育生物学基础理论提供良好的模型,而且可为细胞替代性治疗提供大量的供体细胞。本文以rESCs为主要研究对象,在rESCs定向分化为神经细胞的基础上着重研究神经谱系分化及调控胶质祖细胞迁移的机理。主要结论如下:1) rESCs来源的神经上皮干/前体细胞(NEPs)主要变为辐射状胶质细胞(RG)后再通过中间类型的祖细胞——神经元祖细胞(NPs)和胶质祖细胞(GPs)——分别分化为神经元和胶质细胞。同时,NEPs/RG细胞群具有早期神经管背-腹和前-后轴空间特性。NEPs/RG的维持受Notch和FGFR信号作用。此外,实验中还纯化和鉴定了猕猴胶质限定性前体细胞(GRPs)。结果表明,rESCs的神经谱系分化能够模拟体内发育过程,并与啮齿类动物早期神经谱系变化过程相似。2) 气体信号分子NO(由10μM—250μM SNP供体释放)促进rESCs来源的A2B5+/Nestin/PSA-NCAM胶质祖细胞迁移。进一步研究发现Netrin-DCC信号通路介导了NO启动的细胞迁移过程。同时,Ca2也参与调控胶质祖细胞的迁移。此外,细胞外基质和整合素α6亦可能与Netrin-DCC相互作用调控细胞迁移。结果显示,NO通过激活一个复杂的信号网络系统调控胶质祖细胞迁移。本实验的研究结果有助于揭示灵长类中枢神经系统发育的机理,同时也能为治疗神经系统退行性疾病提供阶段特异性的供体细胞。

Relevância:

80.00% 80.00%

Publicador:

Resumo:

2003 年3 月到2006 年3 月,我们对世界上了解最少的鹤类,也是唯一一种越冬和繁 殖都在高原湿地内进行的鹤类——黑颈鹤(Grus nigrcollis)东部种群的野外繁殖生态、越冬 生态和迁徙路线等方面作了重点研究。研究时间分为三个阶段:2003 年3 月到2005 年6 月,在黑颈鹤的繁殖地点四川省若尔盖湿地国家级自然保护区内(102°29′-102°59′E, 33°25′-34°00′N)进行,对在若尔盖湿地内繁殖和度夏黑颈鹤的种群现状,繁殖习 性,繁殖季节黑颈鹤栖息地选择利用及牛羊放牧活动对黑颈鹤栖息地利用的影响,繁殖黑 颈鹤鸟巢及筑巢栖息地选择的特点等内容进行了研究;第二阶段从2004 年10 月到2006 年3 月,在黑颈鹤东部种群重要的越冬地云南省大山包黑颈鹤国家级自然保护区内 (103o14’55”—103o18’38”E, 27º18’38”—27o28’42”N)进行,对越冬黑颈鹤的越冬习性,栖息 地选择利用,白昼时间行为分配进行了研究;第三阶段2005 年2 月-3 月、2006 年3 月,在云南省大山包保护区和贵州省草海黑颈鹤国家级自然保护区,给8 只黑颈鹤佩戴卫 星发射器,第一次在中国利用卫星技术来跟踪候鸟的迁徙,对东部黑颈鹤越冬种群的迁徙 路线进行求证和新的探索,并利用卫星数据进行黑颈鹤在繁殖地和越冬地活动特点的分 析。 在2004 年5 月围绕整个若尔盖湿地自然保护区内和周边地区繁殖和度夏黑颈鹤的现 状调查中,共统计到黑颈鹤320 只和巢6 个,112 只黑颈鹤(35%)和5 个鸟巢分布在保护 区内,主要集中在保护区内水域和沼泽面积较大的两块核心区内,208 只黑颈鹤(65%)和1 个鸟巢分布在保护区外,主要分布在黄河、白河沿线地区,其中在白河和黄河交界的地 区,记录有163 只黑颈鹤;本次调查中,黑颈鹤利用最多的是在黄河和白河交界处的农 地,其次是沼泽和河岸地带,最少的是草甸和退化草甸;不论是在保护区内还是在保护区 外,湿地生境都体现了黑颈鹤在栖息地选择时的重要性;在花湖繁殖地,黑颈鹤繁殖种群 和巢在3 年内呈现下降和减少的趋势,湿地面积的缩小和退化可能是主要的原因。 繁殖习性:根据繁殖期间产卵,幼鹤出壳等事件行为发生的时间将整个繁殖季节划分 为繁殖前期(到达之日到5 月12 日),繁殖中期(5 月13 日到6 月18 日)和繁殖后期(6 月19 日到离开)。黑颈鹤3 月下旬即从越冬地返回繁殖地点花湖,首先到达的是带有幼鹤的繁 殖家庭鹤,之后才是集群鹤,这种返回的过程持续到5 月初。在繁殖前期,黑颈鹤种群数 量经历一个增加的过程,在此期间,花湖的黑颈鹤种群数量较低(27),繁殖黑颈鹤先后经历家庭解体 (Family breakup),建立繁殖领域,完成交配,筑巢等行为,进入繁殖中期 后,花湖的黑颈鹤种群数量整体呈现下降趋势,并在6 月的第一周达到最低,繁殖中期黑 颈鹤的种群比前期稍高(29),与繁殖相关的行为在整个繁殖季节达到最高(51%),进入繁 殖后期,随着幼鹤出壳和成鹤维持领域能力的降低,花湖周围的黑颈鹤种群数量再次增 加,并在以后的2 个月内维持在较高的数量(56),到9 月中旬,黑颈鹤开始迁徙,4 周 后,所有的鹤都离开繁殖地花湖。在繁殖期间,被驱逐出领域的幼鹤与非繁殖的成鹤形成 集群在繁殖地周围游荡,集群在各个时期都存在,只是在繁殖前期最多(2 群/周),繁殖中 期和繁殖后期为1 群/周,群内个体数量在繁殖中期最高(26 只/群),在繁殖前期和中期分 别是6 和8 只/群,不同时期的群体和群体规模都存在显著差异;黑颈鹤的交配发起者是 雌鹤,交配的成功率为60%,雄鹤的无应答和不成熟的交配经验是交配失败的主要原 因,80%的交配发生在上午,交配成功率为58.3%,20%的交配发生在下午,成功率为 66.7%,黑颈鹤的交配主要发生在4 月到5 月上旬之间,66.7%的交配发生在这一时期, 成功率为80%,之后到6 月上旬的交配仅有33.3%,成功率仅有20%,随着时间的推移, 交配的成功率降低(从4 月的100%减少到5 月份的45%和6 月份的0);黑颈鹤的窝卵数是 2 枚,卵重207 克,卵长径和短径分别是107 和58 毫米,孵卵期为31 天,幼鹤的出壳率 为100%,但二个月后的死亡率达到31.2%,之后的幼鹤未观察到死亡,幼鹤出壳后两个 月内的死亡率可能是制约种群增长的一个原因;繁殖期间黑颈鹤食物以蕨麻(Potentilla anserina)、荸荠(Heleocharis dulcis)、委陵菜属(Comarum)、草地早熟禾(Poa pratensis)、眼 子菜属(Potamageton)、蒲公英(Taraxacum mongolicum)等植物的花、果、茎等为主,但也 取食包括无脊椎动物如蝗虫(Chorthippus hsiai),粪金龟(Geotrupes sp.),椭圆萝卜螺(Radix swinboi)和耳萝卜螺(Radix ouricuaria),以及脊椎动物黑唇鼠兔(Ochotona curizoniae)、红 脚鹬(Tringa totanus)、黑水鸡(Callinula chloropus)、小..(Tachgbaptus ruficollis)、黄河裸 鲤(Gymnocypris pylzovi)等,取食动物性食物可能是补充繁殖所耗费的巨大能量和为迁徙 储备能量;繁殖季节黑颈鹤的主要时间分配在取食和繁殖上,分别占45%和28%,其余 依次为运动10%、护理9%、警戒6%、静息1%和其它1%,不同的繁殖阶段,除了运动 和其它行为外,其余各种行为的时间分配存在显著差异,各行为频次以警戒最高(43 次/小 时),其余依次为取食(31 次/小时)、护理(17 次/小时)、运动(11 次/小时)、繁殖(5 次/小 时)、其它(1 次/小时)和静息(1 次/小时),除了其它行为外,各繁殖阶段行为发生频次差异 显著,各行为的持续时间以繁殖最多(189 秒/次),其次为取食(53 秒/次)、静息(50 秒/次)、 运动(33 秒/次)、其它(22 秒/次)和护理(19 秒/次),在一天中,黑颈鹤各行为分配随时间的历家庭解体 (Family breakup),建立繁殖领域,完成交配,筑巢等行为,进入繁殖中期 后,花湖的黑颈鹤种群数量整体呈现下降趋势,并在6 月的第一周达到最低,繁殖中期黑 颈鹤的种群比前期稍高(29),与繁殖相关的行为在整个繁殖季节达到最高(51%),进入繁 殖后期,随着幼鹤出壳和成鹤维持领域能力的降低,花湖周围的黑颈鹤种群数量再次增 加,并在以后的2 个月内维持在较高的数量(56),到9 月中旬,黑颈鹤开始迁徙,4 周 后,所有的鹤都离开繁殖地花湖。在繁殖期间,被驱逐出领域的幼鹤与非繁殖的成鹤形成 集群在繁殖地周围游荡,集群在各个时期都存在,只是在繁殖前期最多(2 群/周),繁殖中 期和繁殖后期为1 群/周,群内个体数量在繁殖中期最高(26 只/群),在繁殖前期和中期分 别是6 和8 只/群,不同时期的群体和群体规模都存在显著差异;黑颈鹤的交配发起者是 雌鹤,交配的成功率为60%,雄鹤的无应答和不成熟的交配经验是交配失败的主要原 因,80%的交配发生在上午,交配成功率为58.3%,20%的交配发生在下午,成功率为 66.7%,黑颈鹤的交配主要发生在4 月到5 月上旬之间,66.7%的交配发生在这一时期, 成功率为80%,之后到6 月上旬的交配仅有33.3%,成功率仅有20%,随着时间的推移, 交配的成功率降低(从4 月的100%减少到5 月份的45%和6 月份的0);黑颈鹤的窝卵数是 2 枚,卵重207 克,卵长径和短径分别是107 和58 毫米,孵卵期为31 天,幼鹤的出壳率 为100%,但二个月后的死亡率达到31.2%,之后的幼鹤未观察到死亡,幼鹤出壳后两个 月内的死亡率可能是制约种群增长的一个原因;繁殖期间黑颈鹤食物以蕨麻(Potentilla anserina)、荸荠(Heleocharis dulcis)、委陵菜属(Comarum)、草地早熟禾(Poa pratensis)、眼 子菜属(Potamageton)、蒲公英(Taraxacum mongolicum)等植物的花、果、茎等为主,但也 取食包括无脊椎动物如蝗虫(Chorthippus hsiai),粪金龟(Geotrupes sp.),椭圆萝卜螺(Radix swinboi)和耳萝卜螺(Radix ouricuaria),以及脊椎动物黑唇鼠兔(Ochotona curizoniae)、红 脚鹬(Tringa totanus)、黑水鸡(Callinula chloropus)、小..(Tachgbaptus ruficollis)、黄河裸 鲤(Gymnocypris pylzovi)等,取食动物性食物可能是补充繁殖所耗费的巨大能量和为迁徙 储备能量;繁殖季节黑颈鹤的主要时间分配在取食和繁殖上,分别占45%和28%,其余 依次为运动10%、护理9%、警戒6%、静息1%和其它1%,不同的繁殖阶段,除了运动 和其它行为外,其余各种行为的时间分配存在显著差异,各行为频次以警戒最高(43 次/小 时),其余依次为取食(31 次/小时)、护理(17 次/小时)、运动(11 次/小时)、繁殖(5 次/小 时)、其它(1 次/小时)和静息(1 次/小时),除了其它行为外,各繁殖阶段行为发生频次差异 显著,各行为的持续时间以繁殖最多(189 秒/次),其次为取食(53 秒/次)、静息(50 秒/次)、 运动(33 秒/次)、其它(22 秒/次)和护理(19 秒/次),在一天中,黑颈鹤各行为分配随时间的历家庭解体 (Family breakup),建立繁殖领域,完成交配,筑巢等行为,进入繁殖中期 后,花湖的黑颈鹤种群数量整体呈现下降趋势,并在6 月的第一周达到最低,繁殖中期黑 颈鹤的种群比前期稍高(29),与繁殖相关的行为在整个繁殖季节达到最高(51%),进入繁 殖后期,随着幼鹤出壳和成鹤维持领域能力的降低,花湖周围的黑颈鹤种群数量再次增 加,并在以后的2 个月内维持在较高的数量(56),到9 月中旬,黑颈鹤开始迁徙,4 周 后,所有的鹤都离开繁殖地花湖。在繁殖期间,被驱逐出领域的幼鹤与非繁殖的成鹤形成 集群在繁殖地周围游荡,集群在各个时期都存在,只是在繁殖前期最多(2 群/周),繁殖中 期和繁殖后期为1 群/周,群内个体数量在繁殖中期最高(26 只/群),在繁殖前期和中期分 别是6 和8 只/群,不同时期的群体和群体规模都存在显著差异;黑颈鹤的交配发起者是 雌鹤,交配的成功率为60%,雄鹤的无应答和不成熟的交配经验是交配失败的主要原 因,80%的交配发生在上午,交配成功率为58.3%,20%的交配发生在下午,成功率为 66.7%,黑颈鹤的交配主要发生在4 月到5 月上旬之间,66.7%的交配发生在这一时期, 成功率为80%,之后到6 月上旬的交配仅有33.3%,成功率仅有20%,随着时间的推移, 交配的成功率降低(从4 月的100%减少到5 月份的45%和6 月份的0);黑颈鹤的窝卵数是 2 枚,卵重207 克,卵长径和短径分别是107 和58 毫米,孵卵期为31 天,幼鹤的出壳率 为100%,但二个月后的死亡率达到31.2%,之后的幼鹤未观察到死亡,幼鹤出壳后两个 月内的死亡率可能是制约种群增长的一个原因;繁殖期间黑颈鹤食物以蕨麻(Potentilla anserina)、荸荠(Heleocharis dulcis)、委陵菜属(Comarum)、草地早熟禾(Poa pratensis)、眼 子菜属(Potamageton)、蒲公英(Taraxacum mongolicum)等植物的花、果、茎等为主,但也 取食包括无脊椎动物如蝗虫(Chorthippus hsiai),粪金龟(Geotrupes sp.),椭圆萝卜螺(Radix swinboi)和耳萝卜螺(Radix ouricuaria),以及脊椎动物黑唇鼠兔(Ochotona curizoniae)、红 脚鹬(Tringa totanus)、黑水鸡(Callinula chloropus)、小..(Tachgbaptus ruficollis)、黄河裸 鲤(Gymnocypris pylzovi)等,取食动物性食物可能是补充繁殖所耗费的巨大能量和为迁徙 储备能量;繁殖季节黑颈鹤的主要时间分配在取食和繁殖上,分别占45%和28%,其余 依次为运动10%、护理9%、警戒6%、静息1%和其它1%,不同的繁殖阶段,除了运动 和其它行为外,其余各种行为的时间分配存在显著差异,各行为频次以警戒最高(43 次/小 时),其余依次为取食(31 次/小时)、护理(17 次/小时)、运动(11 次/小时)、繁殖(5 次/小 时)、其它(1 次/小时)和静息(1 次/小时),除了其它行为外,各繁殖阶段行为发生频次差异 显著,各行为的持续时间以繁殖最多(189 秒/次),其次为取食(53 秒/次)、静息(50 秒/次)、 运动(33 秒/次)、其它(22 秒/次)和护理(19 秒/次),在一天中,黑颈鹤各行为分配随时间的历家庭解体 (Family breakup),建立繁殖领域,完成交配,筑巢等行为,进入繁殖中期 后,花湖的黑颈鹤种群数量整体呈现下降趋势,并在6 月的第一周达到最低,繁殖中期黑 颈鹤的种群比前期稍高(29),与繁殖相关的行为在整个繁殖季节达到最高(51%),进入繁 殖后期,随着幼鹤出壳和成鹤维持领域能力的降低,花湖周围的黑颈鹤种群数量再次增 加,并在以后的2 个月内维持在较高的数量(56),到9 月中旬,黑颈鹤开始迁徙,4 周 后,所有的鹤都离开繁殖地花湖。在繁殖期间,被驱逐出领域的幼鹤与非繁殖的成鹤形成 集群在繁殖地周围游荡,集群在各个时期都存在,只是在繁殖前期最多(2 群/周),繁殖中 期和繁殖后期为1 群/周,群内个体数量在繁殖中期最高(26 只/群),在繁殖前期和中期分 别是6 和8 只/群,不同时期的群体和群体规模都存在显著差异;黑颈鹤的交配发起者是 雌鹤,交配的成功率为60%,雄鹤的无应答和不成熟的交配经验是交配失败的主要原 因,80%的交配发生在上午,交配成功率为58.3%,20%的交配发生在下午,成功率为 66.7%,黑颈鹤的交配主要发生在4 月到5 月上旬之间,66.7%的交配发生在这一时期, 成功率为80%,之后到6 月上旬的交配仅有33.3%,成功率仅有20%,随着时间的推移, 交配的成功率降低(从4 月的100%减少到5 月份的45%和6 月份的0);黑颈鹤的窝卵数是 2 枚,卵重207 克,卵长径和短径分别是107 和58 毫米,孵卵期为31 天,幼鹤的出壳率 为100%,但二个月后的死亡率达到31.2%,之后的幼鹤未观察到死亡,幼鹤出壳后两个 月内的死亡率可能是制约种群增长的一个原因;繁殖期间黑颈鹤食物以蕨麻(Potentilla anserina)、荸荠(Heleocharis dulcis)、委陵菜属(Comarum)、草地早熟禾(Poa pratensis)、眼 子菜属(Potamageton)、蒲公英(Taraxacum mongolicum)等植物的花、果、茎等为主,但也 取食包括无脊椎动物如蝗虫(Chorthippus hsiai),粪金龟(Geotrupes sp.),椭圆萝卜螺(Radix swinboi)和耳萝卜螺(Radix ouricuaria),以及脊椎动物黑唇鼠兔(Ochotona curizoniae)、红 脚鹬(Tringa totanus)、黑水鸡(Callinula chloropus)、小..(Tachgbaptus ruficollis)、黄河裸 鲤(Gymnocypris pylzovi)等,取食动物性食物可能是补充繁殖所耗费的巨大能量和为迁徙 储备能量;繁殖季节黑颈鹤的主要时间分配在取食和繁殖上,分别占45%和28%,其余 依次为运动10%、护理9%、警戒6%、静息1%和其它1%,不同的繁殖阶段,除了运动 和其它行为外,其余各种行为的时间分配存在显著差异,各行为频次以警戒最高(43 次/小 时),其余依次为取食(31 次/小时)、护理(17 次/小时)、运动(11 次/小时)、繁殖(5 次/小 时)、其它(1 次/小时)和静息(1 次/小时),除了其它行为外,各繁殖阶段行为发生频次差异 显著,各行为的持续时间以繁殖最多(189 秒/次),其次为取食(53 秒/次)、静息(50 秒/次)、 运动(33 秒/次)、其它(22 秒/次)和护理(19 秒/次),在一天中,黑颈鹤各行为分配随时间的历家庭解体 (Family breakup),建立繁殖领域,完成交配,筑巢等行为,进入繁殖中期 后,花湖的黑颈鹤种群数量整体呈现下降趋势,并在6 月的第一周达到最低,繁殖中期黑 颈鹤的种群比前期稍高(29),与繁殖相关的行为在整个繁殖季节达到最高(51%),进入繁 殖后期,随着幼鹤出壳和成鹤维持领域能力的降低,花湖周围的黑颈鹤种群数量再次增 加,并在以后的2 个月内维持在较高的数量(56),到9 月中旬,黑颈鹤开始迁徙,4 周 后,所有的鹤都离开繁殖地花湖。在繁殖期间,被驱逐出领域的幼鹤与非繁殖的成鹤形成 集群在繁殖地周围游荡,集群在各个时期都存在,只是在繁殖前期最多(2 群/周),繁殖中 期和繁殖后期为1 群/周,群内个体数量在繁殖中期最高(26 只/群),在繁殖前期和中期分 别是6 和8 只/群,不同时期的群体和群体规模都存在显著差异;黑颈鹤的交配发起者是 雌鹤,交配的成功率为60%,雄鹤的无应答和不成熟的交配经验是交配失败的主要原 因,80%的交配发生在上午,交配成功率为58.3%,20%的交配发生在下午,成功率为 66.7%,黑颈鹤的交配主要发生在4 月到5 月上旬之间,66.7%的交配发生在这一时期, 成功率为80%,之后到6 月上旬的交配仅有33.3%,成功率仅有20%,随着时间的推移, 交配的成功率降低(从4 月的100%减少到5 月份的45%和6 月份的0);黑颈鹤的窝卵数是 2 枚,卵重207 克,卵长径和短径分别是107 和58 毫米,孵卵期为31 天,幼鹤的出壳率 为100%,但二个月后的死亡率达到31.2%,之后的幼鹤未观察到死亡,幼鹤出壳后两个 月内的死亡率可能是制约种群增长的一个原因;繁殖期间黑颈鹤食物以蕨麻(Potentilla anserina)、荸荠(Heleocharis dulcis)、委陵菜属(Comarum)、草地早熟禾(Poa pratensis)、眼 子菜属(Potamageton)、蒲公英(Taraxacum mongolicum)等植物的花、果、茎等为主,但也 取食包括无脊椎动物如蝗虫(Chorthippus hsiai),粪金龟(Geotrupes sp.),椭圆萝卜螺(Radix swinboi)和耳萝卜螺(Radix ouricuaria),以及脊椎动物黑唇鼠兔(Ochotona curizoniae)、红 脚鹬(Tringa totanus)、黑水鸡(Callinula chloropus)、小..(Tachgbaptus ruficollis)、黄河裸 鲤(Gymnocypris pylzovi)等,取食动物性食物可能是补充繁殖所耗费的巨大能量和为迁徙 储备能量;繁殖季节黑颈鹤的主要时间分配在取食和繁殖上,分别占45%和28%,其余 依次为运动10%、护理9%、警戒6%、静息1%和其它1%,不同的繁殖阶段,除了运动 和其它行为外,其余各种行为的时间分配存在显著差异,各行为频次以警戒最高(43 次/小 时),其余依次为取食(31 次/小时)、护理(17 次/小时)、运动(11 次/小时)、繁殖(5 次/小 时)、其它(1 次/小时)和静息(1 次/小时),除了其它行为外,各繁殖阶段行为发生频次差异 显著,各行为的持续时间以繁殖最多(189 秒/次),其次为取食(53 秒/次)、静息(50 秒/次)、 运动(33 秒/次)、其它(22 秒/次)和护理(19 秒/次),在一天中,黑颈鹤各行为分配随时间的变化而体现较为明显的节律性,这可能与青藏高原恶劣的自然环境(如高辐射和热量的不 均匀分布)有关。 2003 年4 月1 日到10 月13 日,在花湖对黑颈鹤繁殖栖息地选择和放牧活动对黑颈鹤 取食栖息地选择的影响进行研究。研究区域内,按照从湖心向外的方向,将黑颈鹤繁殖期 间所使用的生境划分为4 种类型,即:湖心沼泽,浅水沼泽,草甸和退化草甸。繁殖期 间,黑颈鹤对各种栖息地利用的强度并非一致。湖心沼泽和湖岸沼泽是整个繁殖季节黑颈 鹤青睐的栖息地,是黑颈鹤筑巢和休息的地点,草甸和退化草甸是黑颈鹤主要的取食地 点,但在整个季节内都不是黑颈鹤青睐的栖息地类型,虽然在繁殖后期,在草甸和退化草 甸上活动的黑颈鹤明显增加。在有牛羊放牧时,大多数的繁殖鹤(49.7%)选择在距离湖边 100m 内的区域活动,而非繁殖鹤则主要在0-100m 区域(33.3%)和>400m 的区域(28.1%) 活动,在牛羊集中活动的200-400m 区域,两种鹤都选择避开,牛羊离开繁殖地点后, 黑颈鹤有向远离湖边方向扩散的趋势,多数的繁殖鹤(54.9%)和非繁殖鹤(52.3%)都在 >400m 的区域活动,虽然距离水面的距离在繁殖鹤活动地点的选择上有一定的影响,但 过度放牧的牛羊的确压缩了繁殖鹤和非繁殖鹤的活动空间。因此,在繁殖地来说,减少沼 泽区域的开发,对特定区域放牧活动的控制,加强沼泽生境的恢复,是保证黑颈鹤成功繁 殖的关键。 2003 年5 月到2005 年6 月,在若尔盖湿地内找到黑颈鹤的巢21 个。黑颈鹤的巢有3 种,分别是芦苇巢(3 个)、地上巢(14 个)和泥堆巢(4 个),地上巢巢参数最小,芦苇巢的巢 参数最大;所有的巢都分布在湿地环境中,包括湖泊,沼泽和河流三种栖息地,巢在这些 栖息地中的分布也不是均匀的,湖泊中分布的巢最多,湖泊是黑颈鹤筑巢首选的栖息地, 但每年在此类生境中筑巢的黑颈鹤正在减少,黑颈鹤选择避开利用沼泽区域作为筑巢的栖 息地,黑颈鹤对河流区域的利用按照获得性进行;筑巢栖息地周围1 米外的草高和巢的暴 露与否、巢距离水面的距离和巢所在草岛的面积、巢周围的水深成为影响巢址选择的三个 主要生态因子,反映了隐蔽度、筑巢栖息地的质量和到达巢的难易程度是黑颈鹤选择巢址 的主要因素;在不同的微生境中,巢的参数不同,湖泊中的巢参数最大,湖泊中的巢比沼 泽中的巢更长、更宽和更高,而巢周围的水深差距不明显,湖泊中的巢要比河流中的巢短 径大,巢周的水深要比河流中的巢要稍浅,但巢长径和巢高差异不显著,沼泽和河流环境 中的巢参数没有明显的差异;巢周围有一定的水深是巢址选择时最为基本的条件;与其他 地区黑颈鹤的巢比较,若尔盖湿地中的巢要更小,但巢周围的水深要更深,这可能与不同 地点的植被、地理环境以及不同的人为干扰强度有关;若尔盖湿地内黑颈鹤巢栖息地的选择是黑颈鹤对正在变化中栖息地的妥协结果,保留有适宜于繁殖的小面积沼泽区域对黑颈 鹤的繁殖也很重要。 2004 年10 月到2006 年3 月,在大山包保护区对越冬黑颈鹤的生态进行研究。我们 将整个越冬季节划分为越冬早期(10 月-12 月),越冬中期(1 月-2 月)和越冬后期(3 月-4 月)。保护区内黑颈鹤利用的栖息地划分为4 种类型,即:浅水生境,沼泽区域,草甸和 耕地。首先到达越冬地的仍然是家庭鹤,其次是集群鹤。大山包是黑颈鹤春季迁徙和秋季 迁徙的迁徙中转站,迁徙的高峰在12 月和3 月出现,在草海越冬的黑颈鹤在春季迁徙时 经过大山包,并在此停留8 天。大山包也是黑颈鹤的越冬地点,有大约900 只的黑颈鹤在 此越冬。黑颈鹤的配对主要发生在越冬中期,黑颈鹤家庭的解体(Family breakup)发生在繁 殖后期的3 月和4 月间,成鹤以放弃幼鹤离开越冬地而达到家庭的解体。整个越冬季节, 黑颈鹤对各种栖息地的利用强度并不是一致的。湿地(浅水区域和沼泽)是黑颈鹤整个冬天 青睐的生境(除了越冬后期对水域区域利用低外),而耕地是越冬早期和越冬中期黑颈鹤的 主要取食地点,在越冬后期,草甸则成为黑颈鹤的主要取食地点。在整个冬天,幼鹤将 72.2%的时间用在取食,将6.8%的时间用在警戒,将18.6%的时间用在修整行为上,用在 其它行为上的时间为2.4%,而成鹤用在这些行为上的时间分配是63.9%,11%,22.8%和 2.3%。随着时间的推移,成鹤减少取食的时间,与之对应而增加了修整行为的比例,而 幼鹤的各行为变化没有规律性。是否具有越冬经验和不同的生态需求导致了成鹤和幼鹤的 不同时间分配。正是由于具有越冬经验,成鹤能够有效地调整不同行为的分配,幼鹤虽然 没有越冬经验,但在成鹤的照顾下,幼鹤有足够长的时间去取食,成鹤和幼鹤采取了不同 的越冬策略。正是具有越冬经验,成鹤的白昼行为分配呈现出一定的规律性,如取食行为 在早晚各自有一个取食峰值,而修整行为在中午最高等,而由于缺乏越冬经验和行为受到 成鹤的影响较大,幼鹤的行为节律规律性不是很强。 2005 年2-3 月和2006 年3 月,在大山包和贵州草海给8 只黑颈鹤放置了卫星发射器 以确定这两个地点的黑颈鹤的迁徙路线和新的繁殖地点。东部越冬种群的黑颈鹤迁徙时间 2-4 天,中途停歇3-4 个点,迁徙平均距离为622 公里,黑颈鹤迁徙时首先飞越金沙 江,向北偏西方向穿过和停歇于四川省的凉山山脉,到达凉山、邛崃山和大雪山脉交界的 地方,然后沿着大渡河河谷向北迁徙,到达包括四川省的若尔盖县、红原县、阿坝县、松 潘县,以及甘肃省玛曲县的若尔盖湿地内。与1993 年环志证实的迁徙路线比较,黑颈鹤 迁徙时明显避开了海拔较低、人口稠密的四川盆地,选择了沿着青藏高原东缘向四川盆地 过渡的高山峡谷地带飞行,沿着大渡河河谷进行迁徙。2 只黑颈鹤的信号在大渡河河谷区域消失,这个地点对于黑颈鹤的迁徙和保护有重要的意义。到达繁殖地后,黑颈鹤的活动 范围在5 月达到最大,此后逐渐减小,在8 月份活动范围减小到最小,之后,活动面积又 逐渐增大,并在迁徙前达到最高。在繁殖地,黑颈鹤每天的活动范围只有不到2km,隔 日的活动范围也不超过3km,结果提示在若尔盖湿地内可能还有更多的黑颈鹤活动。编 号为55984 的黑颈鹤在2005 年11 月和2006 年3 月分别完成从繁殖地返回越冬地和从越 冬地再次到达繁殖地的迁徙过程,在草海环志的64311 在繁殖地若尔盖湿地度过繁殖季节 后又成功返回草海越冬,而64310 在大山包越冬,在若尔盖湿地内度过夏季,在2006 年 11 月又返回草海越冬,其余两只黑颈鹤返回大山包越冬,结果证实1、黑颈鹤迁徙路线、 繁殖地和越冬地选择的稳定性,2、东部黑颈鹤越冬种群存在交流。

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Diagonal self-assembled InAs quantum wire (QWR) arrays with the stacked InAs/In0.52Al0.48As structure are grown on InP substrates, which are (001)-oriented and misoriented by 6degrees towards the [100] direction. Both the molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE) techniques are employed. Transmission electron microscopy reveals that whether a diagonal InAs QWR array of the stacked InAs/InAlAs is symmetrical about the growth direction or not depends on the growth method as well as substrate orientation. Asymmetry in the diagonal MEE-grown InAs QWR array can be ascribed to the influence of surface reconstruction on upward migration of adatoms during the self-assembly of the InAs quantum wires.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

本文利用Level Set方法,数值模拟了微重力情况下气泡/液滴的Marangoni迁移现象,分析了Marangoni数对迁移速度的影响.数值模拟结果表明,随着Marangoni数的增大,非线性热对流效应的影响会逐渐增大,导致沿相界面温度分布趋于均匀,从而降低迁移运动的驱动力,使气泡/液滴的迁移速度随Marangoni数的增加而逐渐减小.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

揭示水体中繁殖的两栖动物在异质性景观中的空间扩散特点,探讨景观面积丧失和破碎化对于两栖动物的影响,为两栖动物的保护提供理论依据。本文以四川西北部若尔盖湿地自然保护区的高原林蛙(Rana kukunoris)为研究对象,通过运用地理信息系统及建立景观模型等方法,在分析若尔盖湿地自然保护区范围内现有景观格局的基础上,建立了高原林蛙的景观扩散模型,并模拟了“沼泽→草甸”的湿地逆演化过程下高原林蛙的空间分布与景观连接的变化特点。主要结果是: 1.若尔盖湿地自然保护区呈典型的沼泽—草甸式斑块—基质景观格局。草甸面积占整个景观面积的79.42%,景观蔓延度指数(CONTAG)为79.00远离最小值0而更趋向于最大值100,面积和景观蔓延度指数表明草甸是整个景观中面积占绝对优势且景观连接好的类型,构成了景观的基质,对景观的动态格局演变起主导作用。沼泽面积仅占整个景观面积的18.08%,但却是整个景观中斑块数目最多的单元,占所有斑块数的82.9%。因此沼泽斑块与草甸基质之间的动态结构对高原林蛙的扩散起着决定性的作用。 2.空间扩散模型表明,其它类型的景观不但扩展了高原林蛙的活动范围,而且也为高原林蛙在不同沼泽斑块间的连接提供了通道。高原林蛙的空间扩散区域使得彼此间成斑块化隔离状分布的沼泽形成了潜在景观功能连接,促进了不同斑块间物种的交流。小型沼泽作为垫脚石(stepping-stone),使得整个景观中的相隔距离较远的大型斑块联结为一个功能整体,促进了高原林蛙在整个景观中的相互动态联系。 3.模拟“沼泽→草甸”的湿地逆演化过程表明,大量小型沼泽湿地的消失将会 对在沼泽中繁殖并扩散到其它景观类型中去的高原林蛙造成潜在影响。逆演化过程不仅使沼泽斑块的分布范围,沼泽源斑块的面积和空间扩散面积减少,而且对景观连接也有很大影响。小型沼泽的消失,将使得景观斑块的功能连接变小,使得依靠小型沼泽作为跳板的动物在沼泽斑块之间的移动将变得更加困难。 本文是对生境丧失与破碎化影响下两栖动物的行为反应的一种尝试。影响模型的因素很多,包括动物对各种类型景观的偏好程度,地理数据的精度,及模型的可靠程度都是制约模型准确度的因素。 The spatial diffusion of water—breeding amphibian through heterogeneous landscape and the effects of landscape losing and fragmentation to amphibian were the core theory of the landscape ecology of amphibian. Geographical information system (GIS) and landscape model were used to model the diffused area of Rana kukunoris in Zoige Wetland Natural Reserve. Model was also used to analysis the spatial distribution variation of R. kukunoris and the change of landscape connectivity when simulated the retrogressive succession of landscape. The main results are below: 1. There was peatland—meadow pattern which was typical patch—matrix landscape pattern in Zoige Natural Reserve. The meadow area occupied 79.42% of the entire landscape area, contagion index (CONTAG) was 79.00 which was far away the minimum value (0) but tend to the maximum value (100). Both of these showed that meadow was the largest part and the most continue units. It was shown that meadow was matrix of the landscape, which evolved the leading role to the landscape dynamic pattern. Though their area only occupies 18.08% of entire landscape area, peatlands were according to 82.9% of the total patches. Dynamic of the pattern between peatlands and meadows decided the spatial diffusion of R. kukunoris. 2.The model indicated that the other types of landscape not only expanded diffusion of R. kukunoris, but also have provided the potential channels for frog's connections among different peatlands. The spatial diffusion zone of R. kukunoris forced isolated patch peatlands to be potential landscape functional connectivity. The small peatlands, as stepping-stone, made the large peatlands connect as a functional one and promoted the integrated and dynamic connectivity of R. kukunoris in the whole landscape. 3. The simulation of “peatlands→meadows”retrogressive succession process indicated that the decrease of small peatlands will have potential effect to R. kukunoris because they must bred in peatlands and diffuse to other type of the landscape. Retrogressive succession process not only made the decrease of distribution of peatlands, patches number of peatlands and diffused area of R. kukunoris, but also reduced the connectivity among source patches. As stepping-stone, the disappearance of small peatlands will made the migration of R. kukunoris among patches more difficult. The model was an experiment of the amphibian behavior reaction to habitat losing and fragmentation. There were many factors that could influence the accuracy of model, such as the preference of animals to each type of landscape, the geographical data precision, reliable degree of model.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

genetics, such as: population size, reproduction, mating system, growth, development,genetic structure and systematics status; The main results are presented below: The seasonal variation of the operational sexual ratio of this animal was found in the field and the ration always bias the female in the breeding season. Aiming at this character and considering the distance of time and space of both sexual habitat in breeding season, we census female population first by toe-clipping mark-recapture method, then estimated the population size with the definitive sexual ratio. Up to now, this species was found only at the Beilun district of the Ningbo City. The population size of the Ruiyan Temple Forest Park approximates to 369. The status of this population is extremely endangered, so besides protecting this population at the original locality, we also suggested to breed the salamander in fenced locality and to hatch embryos artificially, and send metamorphosed juveniles back to nature. We can transfer some individuals to other similar habitats or breed them under artificial conditions for saving this species from extinction. The early developmental stage of the Chinhai salamander is the same as its relative species, E. andersoni. Their balanceres are poorly developed and disappear very early. Temperature and moisture significantly influence the embryonic development of the Chinhai salamander. The embryonic stage is approx. 29 days under room temperature. The hatchling grows in a logarithmic curve. The larvae stage in water is approx. 58- 88 days. Many factors influence the nomal development, including two aspects of internal and external. Due to these factors, the effective protected measures were presented in detail. The breeding migration of E. chinhaiensis takes place at late March~late April every year. This salamander's hatching rate is high, but the rate of hatchling migrating into water is low. The average effectiveness of all the nest sites is 36.7%. The maternal self-conservation was contrary to the reproductive success of the egg-laying strategy. In the strategy of egg-laying behavior, the first factor selected by the female was its self-conservation, the second is embryonic survival rate, and the last is rate of hatchling survival rate. The oviposition selection is significant for the survival of the larvae. Based on the analysis of the evolutionary process of reproductive behaviors nad egg-laying site selections of all genera of the family Salamandridae, we deduced that perhaps Echinotriton is a transitional type in the evolutionary process from water to land. Due to its location in the adaptive stage in the terrestrial evolution, Echinotriton chinhaiensis's terrestrial nest may be one of important reason that causes this species to be endangered. The genetic deversity analysis shows that although the population size of the Chinhai salamander is quite small compared to other Chinese salamandrid species, the genetic diversity of this population is not reduce remarkably. We explain this phenomena with the polygamy mating system of this species. The result of 4 families' parenthood determinations shows that the parenhood determination can be taken without any paternal information. The "children" of every female include rich genetic information from at least two "fathers". It implies that female Chinhai salamander mates more than once with different males in a breeding season. The molecular evidence, the behavioral observation evidences and the sperm evidence in the female cloaca proved that this species has a polygamy mating system. The kin recognition in the mating of adult salamander was first discussed. The taxonomic status and phylogenetic relationships of 12 species representing 6 genera in the family Salamandridae were studied using DNA fingerprinting. The results showed that the DNA fingerprinting. The results showed that the DNA fingerprinting patterns demonstrated rich genetic diversity and species diversity, and also revealed the taxonomic status and phylogenetic relationshipes of higher taxa to a certain extent. The results are highly consistent with those obtained from the studies based on the morphology, ecology, cytology and molecular biology. The compreshensive analysis indicate that Tylototrition hainanensis and T. wenxianensis should be valid species; Echinotriton should be a valid genus;Tylotortriton is a natural cluster; Tylotortriton asperrimus should be put in Tylototrition rather than in Echinotriton, Hypselotriton and Allomestriton are synonyms of Cynops and Paramesotriton, respectively. There are three main groups in Chinese salamandride: Cynops, Paramesotriton and Pachytrition from the first group, the species of the Tylototriton from the second, and E. chinhaiensis composes the third.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

本文考察了若尔盖高寒泥炭湿地公路对高原林蛙(Rana kukunoris)、倭蛙(Narorana pleskei)和岷山蟾蜍(Bufo minshanicus)的生态影响。分析了公路对两栖动物空间分布和栖息地利用的影响,并用IBM模型探讨其可能作用机制,考察了两栖动物公路死亡的季节差异及影响公路死亡空间分布的景观因素。最后通过对若尔盖高寒湿地两栖动物陆地核心栖息地的分析,为若尔盖路域栖息地的管理提供依据。 1. 对公路周边6个沼泽水凼群进行了调查,每个样地设置5条样线(距离公路10m、20m、50m、100m和150m)。调查表明,在繁殖季节(5月),距离公路距离对高原林蛙和倭蛙的相对数量都有显著作用,其效应明显大于其他各项栖息地环境参数。公路导致高原林蛙和倭蛙在公路周边种群密度降低,其相对数量从距离公路100m处到公路边缘一直呈现逐渐降低的趋势。在繁殖季节,若尔盖高寒湿地的公路生态影响域大约在100-150m之间,这一距离远远大于森林栖息地中公路对两栖类的生态影响域(35-40 m)。 在繁殖后期(9月),对公路周边16个草地样点的样线调查表明,公路对周边高原林蛙和倭蛙密度分布并未造成显著影响。 2. 二次模型的拟合表明繁殖季节高原林蛙和倭蛙在公路周边的密度分布符合钟型曲线。前人对森林公路两侧两栖类分布的研究也显示了类似的规律。我们通过基于个体的模型,模拟在了公路边缘100单位距离内的栖息地空间,栖息地环境质量呈梯度变化,动物个体在其中通过随机运动寻找适宜的栖息地。拟合结果表明,动物个体仅仅依照简单的运动规则寻找适宜栖息地,这种活动就可以导致公路周边栖息地中的动物分布曲线出现3个局部峰。公路周边两栖动物的钟型分布曲线可能仅仅是个体寻找适宜栖息地过程中出现的临时性群体分布模式。 3. 在若尔盖高寒湿地,公路交通造成了大量两栖类死亡。但是公路两栖类动物死亡的季节分布很不均匀:5月、8月和9月死亡数量很高,而7月和10月死亡数量却很低。这种季节性差异和两栖类各个生活史阶段的迁移运动有密切的关系。利用景观参数的逻辑斯蒂回归模型显示,距离公路1000-2000m范围内的湿草地比例对三种两栖类公路死亡概率均有很强的贡献。湿草地这一栖息地类型分类中有大量的沼泽水体,是两栖类重要的繁殖点和取食点。两栖类公路死亡概率湿草地的关系从一个侧面表明,要维持一个区域较高的两栖类种群数量,需要1000-2000m半径范围内存在大面积的湿草地。 4. 高原林蛙和岷山蟾蜍不同性别和年龄个体分布点的水体距离存在显著差异。不同种类、年龄的两栖类分布点距离水体距离的差异可能是由于对水体的依赖性造成的。而相同种类、年龄段的个体中,高原林蛙雌性、岷山蟾蜍亚成体和雌性的体重与分布点距水体距离有显著负相关,这可能是因为体重更大的个体对水体的依赖性更弱。考虑到过大的陆地核心栖息地面积在实际保护工作中存在操作上的困难,因此我们认为可以以水体周边90%个体的分布区为低限确定3种两栖类的最小陆地核心栖息地。但是,在同样的水体距离-两栖类密度分布格局下,水体的面积和分形参数对最小陆地核心栖息地半径的确定有一定影响。 Ecological effects of alpine wetland road on Rana kukunoris, Narorana pleskei, Bufo minshanicus was studied in Zoige wetland. The effects of road on distribution of amphibians and its possible underline mechanism was discussed based on empirical data and computer simulation. Road killed amphibians was surveyed in different season and those landscape factor which could have impact on road killing distribution was analyses. Core terrestrial habitat of amphibians in Zoige wetland was discussed in the consideration of conservation management. 1. Six pool groups was investigated in breeding season (May) of R. kukunoris, N. pleskei. Five transects at distance of 10m, 20m, 50m, 100m and 150m from road edge was surveyed in each pool groups. There was a significant effects of distance from road edge on relative counts of R. kukunoris, N. pleskei, which is much important than effects of other environmental factors. Road caused the density of R. kukunoris, N. pleskei decreased from distance of 100m from road to 10m from road. Road ecological effect zone of alpine wetland for amphibians is about 100-150m. It is much wider than those of forest roads, which is about 35-40m. However, studies on 16 grassland near road showed no significant effect of road on amphibians after breeding season (Sep.). 2. Quadratic model fit indicated that the distribution of R. kukunoris and N. Pleskei followed a hump like curve. Previous studies on forest road showed similar results. A 100×100 habitat with gradual environment besides road was simulated with a individual-based model, and animal seek for suitable habitat with stochastic locomotion in it. Simulation results indicated that 3 density peak of animal distribution can emergent followed a simply rules. The hump like density cure could be a temporal swarm pattern during the process of individual seeking for habitat. 3. Road traffic caused mass death of amphibians in Zoige wetland. There was much road killed amphibians in May, Aug and Sep than those in July and Oct. The fluctuation of road kill could be related with migration of amphibians between seasons. Logistic regression of landscape variables indicated that wet grassland in 1000-2000m is essential to predict the probability of road kill. Wet grassland is an important breeding and forage habitat for amphibians. It also indicated that mass wet grassland in 1000-2000m is essential for maintain a big amphibian population. 4. There was significant differences among distance from aquatic site of subadults, female and males of R. kukunoris and B. Minshanicus. Possibly, it was because of their dependence on water. There was a significant negative relationship between distance from aquatic site and individuals body mass. Estimates of core habitat that are too large may make it difficult to establish protective regulations. The smallest suitable terrestrial core habitats were defined as the terrestrial habitats used during migration to and from the wetlands, and for foraging by 90% of any life stage (adults, and subadults) in a season. However, even with the same amphibian distribution pattern along the distance from aquatic sites, the radii of smallest suitable terrestrial core habitats will be varied with the fractal parameters of aquatic site.